This is an attempt to get students thinking about the cellular basis of life.
In general, they tend to think of themselves as being “whole people.” They
can’t picture “cells,” even though we like to imagine that they do. They
think they have some cells inside them, somewhere. This makes it hard for
them to picture things like glycolysis and mitochondrial activity, because
they assume that all of this goes on in their stomachs, and the ATP is sent
around in their bloodstreams. Protein synthesis, of course, is impossible.

The goal here is to have them figure out some basic requirements of cells,
starting with single-celled organisms that “just” eat and grow. Then, we
consider an additional feature: two cells being able to communicate with
each other, recognize that they are different cell types, contact one another,
stick together, and fuse into a zygote. Then, we add a community of cells
that have different functions, and have to cooperate with each other. Lastly,
we consider humans, which are simply a more complex community of cells.

From this, we hope to get the idea that “food” is stuff we have to digest into
small molecules that single cells can handle, and then send those molecules
around to each of the cells.